This prospective longitudinal study investigates early social and communication development in infants at varying risk for autism spectrum disorder (ASD), with a focus on younger siblings of children with autism who are at high genetic risk. A total of 235 infants were enrolled beginning in 2001, recruited through advertising and from the Kennedy Krieger Institute and the Lurie Center at Massachusetts General Hospital in the United States of America. Children were excluded if they had low birth weight, significant medical complications, or came from non-English-speaking households. The study initially followed children from 14 to 24 months, but from 2003 onwards, the observation period was extended to cover ages 6 to 36 months, with follow-ups conducted at 6, 14, 18, 24, 30, and 36 months.

Recruitment is ongoing